Units of the above variety typically include a compact reflector and incandescent projection lamp (e.g., tungsten-halogen) secured therein. Examples are shown in U.S. Pat. Nos. 3,314,331 (Wiley) and 3,639,750 (Anthonijsz). This assembled component is then positioned within a suitable socket-holder member which in turn is located within (or forms part of) the housing of the desired viewer or projector. An example of such a member is illustrated in U.S. Pat. No. 3,789,212 (Wagner).
Understandably, proper alignment of the component within the socket-holder is essential in order to assure optimum light output for the system. Misalignment of the component within the holder in turn can cause misalignment between this member and the remaining parts of the overall system, including particularly the projector's film gate and lens. The deleterious result is insufficient exposure of the subject item (e.g., microfilm) and a corresponding inadequate illumination on the screen located some distance from the projector.
Another critical parameter for such systems, particularly microfilm viewers, is operating temperature. Typically, incandescent projection lamps operate at relatively high temperatures, making heat dissipation essential. Otherwise, the expected life for such lamps will be drastically curtailed. In addition, an uncomfortably warm lamp and reflector component can render removal thereof (e.g., where repair and/or replacement is necessary) very difficult for the system's operator.
It is believed therefore that a projection unit which substantially eliminates many of the foregoing and related problems and disadvantages of existing such units would constitute a significant advancement in the art.